


A Study in Animagi

by wishingonafeather



Category: Harry Potter - J. K. Rowling, Sherlock (TV)
Genre: Animagus, Catlock, Episode: s01e01 A Study in Pink, Gen, Potterlock
Language: English
Status: In-Progress
Published: 2014-11-10
Updated: 2015-09-23
Packaged: 2018-02-24 21:50:06
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 4,855
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/2597642
Author URL: https://archiveofourown.org/users/wishingonafeather/pseuds/wishingonafeather
Summary: <blockquote class="userstuff">
              <p>When John Watson is invalided home from Afghanistan, he never could have expected to meet Sherlock Holmes. What he expected even less, was to be thrown back into a world that he had long-since abandoned.</p>
            </blockquote>





	1. A New Beginning

**Author's Note:**

> Kudos again to Ariane DeVere on livejournal for the episode transcripts.  
> I'm blaming this entirely on anotherwellkeptsecret.tumblr.com :)

"I play the violin when I'm thinking. Sometimes I don't talk for days on end. Would that bother you? Potential flatmates should know the worst about each other." John Watson barely had the time to process what the man in front of him was saying, his mind still reeling from this stranger's  very rapid and almost impossibly accurate deductions about him.

"The name's Sherlock Holmes and the address is 221B Baker Street. Afternoon." He winked at John before disappearing round the door and out of sight. There was one deduction that Sherlock had only just managed to keep to himself: Muggle.

Sherlock got out of the taxi at Baker Street and headed straight for his makeshift lab, pulling his wand (sycamore with a phoenix core) out of his pocket. With a few simple spells he Vanished his potion kit and any of his magical experiments. He then turned to the bookshelf, Summoning all of his spell books and enchanting them so that, were a muggle to read them, they would appear to be mundane textbooks. Now all he would have to do is pretend that he was going out if he ever wanted to get back on his paws. The thought reminded him of another thing; if he was going to give the impression that he owned a cat (it would give him more leeway when he wanted to lounge about the flat in his animal form), he would need a few props. With a few final flourishes of his wand, a scratching post and food bowls appeared in the flat, and a cat flap was added to the door (Mrs Hudson already had one in her back door in case of emergencies).

There was a sudden knock at the door, and Mrs Hudson, the lovely old witch who owned the building, poked her head around the door, closely followed by John. 

"Well this could be very nice. Very nice indeed." John commented, glancing around the cluttered living room. The human skull on the mantlepiece threw him for a moment, but the rent for this area of London was just too good to miss, and he let it slide; after all, everyone has their own quirks.

"Yes. Yes, I think so. My thoughts precisely." Sherlock replied. The two men spoke at exactly the same time; "So I went straight ahead and moved in."

"Soon as we get this rubbish cleared out .... Oh." John looked a bit sheepish, and Sherlock, for some reason unknown to him, proceeded to pick up a few things in a futile attempt to tidy the room, stabbing his mail to the mantle-piece with a knife.

"I forgot to check. Do you have any allergies?" Sherlock turned to John, an annoyed expression on his face at not being able to deduce something. John thought for a minute.

"None that I'm aware of. Why?"

"There's a cat that pops in now and again. He's perfectly house trained, so you won't even need to clean out his litter tray."

John seemed a bit taken aback. Sherlock, from what he could tell about the man after only having met a few hours ago, was not the sort of person who would own any sort of animal; the kitchen alone was a death-trap, and he hadn't even seen the state of Sherlock's room. It was a miracle the poor thing hadn't been accidently poisoned already, or possibly dissected.

At the moment, Sherlock was distracted by the police sirens outside of the window and he smiled to himself. It looked like another victim of the serial 'suicides' had been found. John turned round as a man (Greg Lestrade, a Detective Inspector judging by the photo staring up at him from yesterday's _The Times_ ) entered the room at a half-jog.

"Where?" Sherlock demanded, without even turning his attention away from the window.

"Brixton. Lauriston Gardens." The DI replied. This brief exchange told John everything he needed to know about the man's connection with his new flatmate; this was obviously a bit of a regular occurrence for Sherlock.

"What's new about this one? You wouldn't have come to get me if there wasn't something different."

"You know how they never leave notes?"

"Yeah?"

"This one did. Will you come?" This caught Sherlock's attention, as he turned round, a glint in his eye.

"Not in a police car. I'll be right behind." With a nod to John and a simple "Thank you" to his new flatmate , Lestrade left them. Once he was out of ear shot, Sherlock sprung into the air, his fist clenched in triumph and catching John completely by surprise.

"Brilliant! Yes! Ah, four serial suicides and now a note! Oh, it's Christmas!" With that he grabbed his coat and scarf, almost sprinting to the door. He paused suddenly, as if a thought had just occurred to him.

"You're a doctor. In fact, you're an army doctor." John got to his feet.

"Yes, what of it?"

"Seen a lot of injuries, then; violent deaths. Bit of trouble too, I bet." John couldn't quite see where this was going, but decided to play along.

"Of course, yes. Enough for a lifetime. Far too much." His nightmares could vouch for that. And then with four small words from Sherlock, John threw caution to the wind.

"Wanna see some more?"

"Oh God, yes."

* * *

Upon arriving at the crime scene Sherlock descended on the corpse like a vulture, looking at every inch of the woman through his magnifying lens. She was fairly elderly, about 60, and dressed in an alarming shade of pink from her lipstick all the way down to her shoes. There was no ID on the body, but there was something familiar about her.

Sherlock launched into a dizzying string of deductions, talking so quickly that John could barely keep up. From what he caught, she was semi-retired, involved in some sort of desk job. She was single, the only jewellery she wore was an ornate golden locket with a large S in emeralds on the front. She was only visiting London for a short time; something about her damp coat and dry umbrella. The only other deduction was that she had suffered from depression for a period of about five years roughly 20 years ago, but this wasn't linked to her apparent suicide.

"You said she left a note?" John asked,turning to face Lestrade, who gestured to the words scratched into the floorboards.

"Vestigo virgola" He read out loud. " What's that about? It sounds Latin." Sherlock thought, before shrugging.

"Unfortunately my knowledge of Latin is not as good as it should be. 'Vestigo' means 'trace', but I have no idea about the latter. It could be the killer mocking us. 'Come and find me before I kill again' sort of thing. I think we're done here. If I think of anything I'll let you know Detective Inspector." He spun around in a dramatic flourish of coat tails and was racing down the stairs, leaving John with his cane to limp behind.

Lestrade's phone pinged, and there was a text from Sherlock.

No wand on the body. Wand with killer. Note spell to track wand. Cast on body and will lead you to killer. -SH

Lestrade smiled; this was one of the few times Sherlock had ever told him something outright, rather than run off and track a suspect down on his own. This case was exactly why Harry Potter, who had quickly risen to the head  of the Auror office, had assigned him to join New Scotland Yard. While most of his cases were of muggle origin, occasionally a witch or wizard was behind it and someone had to cast the odd _Obliviate_ when either one of his own force or a witness had seen anything out of the ordinary. But at the same time, how was he going to use it when the rest of his team would certainly ask how he knew where to go?

* * *

Sherlock was, of course, already tracking the murderer. With his wand up his sleeve he had performed the spell non-verbally. The effect had been an odd sensation of knowing what direction he had to go in, but with no idea of the final destination. As soon as he was out of sight, he twisted his body and vanished with a sharp crack.

Sherlock found himself at Roland-Kerr College. Quickly Apparating back to 221B he grabbed a pen and paper, addressing it to John, with instructions as to where he had to go. You never knew when you would need back-up, and an ex-soldier would certainly come in handy in a fight.

He popped back into existence once again at the college, looking up to the window in one of the laboratories. Jefferson Hope stood there, staring down at him, daring him to come up and play.

* * *

Sherlock sat opposite the old wizard and smiled.

"So you walk in your victims at gun point, and then, what? Let them take their chances with the pills or you gun them down? Not exactly what I'd call genius." Jefferson Hope simply smiled back at him. "So why are you doing this? Oh, of course. You're a dead man walking; delayed action curse most likely. But why kill a bunch of random Muggle-borns? What's in it for you?"

Hope sighed.

"I'm not a rich man, Mr Holmes. My vault at Gringott's is practically bare. But I've got myself a sponsor. He's a big fan of yours, you know - told me all about you, the great Sherlock Holmes. Anyway, the more mudbloods I kill, the more money my children will get when this bloody curse makes its way to my heart."

Sherlock flinched slightly at the term.  "It may have escaped your notice, but your last victim was hardly Muggle-born. But what's the incentive? Either way they stand a high chance of dying." Of course Sherlock was playing for time, and let out an internal sigh of relief as he noticed the small micro-expressions on the cabbie's face, showing that the last of the Felix Felicis he had taken had worn off. Of course that was how he had managed to cheat death four times already.

"My wife was muggleborn. After what that hag put her through, she was always going to be on my list." This confused Sherlock, the man obviously had something against muggleborns, but had then proceeded to marry one. Maybe it was because she had left him, taking his children with her.

"But you still haven't answered my question. What incentive do they have for poisoning themselves?"

"Oh, Mr Holmes, you haven't heard the best part. You see, whichever pill they take, I take the other one." Sherlock paused, pretending to consider his options.

"What if I don't choose either? I _could_ just walk out of here." All too predictably, Hope lifted his gun and pointed it squarely between Sherlock's eyes.

"You can take your fifty-fifty chance, or I can shoot you in the head. Funnily enough, no-one's ever gone for that option."

"I'll have the gun, please." This seemed to throw Hope for a second.

"Are you sure?" Sherlock was still smiling.

"Definitely, the gun." Hope slowly squeezed the trigger, and a small flame burst from the tip.

"I know a real gun when I see one."

Hope reached inside his jacket, and pulled out a slim, jet black wand. Without him saying a single word, Sherlock felt his mind go blissfully blank as the silent Imperius curse hit him. All he could hear was Hope's voice in his head.

_Take the pill nearest me. Take the pill nearest me._

Why not? What harm would it do? Slowly, Sherlock stood up and snatched the bottle and tipped its contents into his palm. He pinched it between two fingers before lowering it to his mouth.

 _Why should I?_ His sluggish brain asked. _He wants you dead, so why do anything he says?_

His hand stopped mere inches from his lips.

Suddenly, a loud _crack_ and the sound of breaking glass caused both of them to turn around. Hope's concentration broken by the bullet that had passed clean through the muscles and blood vessels just above his heart, Sherlock pounced on the man, his own wand at the man's throat.

"Your sponsor. Who was it? The one who told you about me - my 'fan'. I want a name. Hope's voice was weak when he gave a resolute "No". But Sherlock was on a warpath, with fire in his eyes.

"You're dying, but there's still time to hurt you. Give me a name." Hope shook his head, then his eyes widened at the single word that Sherlock spat at him.

" _Crucio!"_

Hope screamed; his back arching as the curse hit him.

"A name! Now!" He directed the curse to focus on Hope's bullet wound. "The NAME!" He almost shouted, white-hot fury in his voice. With the last of his strength, Hope lifted his head and screamed to the heavens.

"MORIARTY!"

His head slumped, his eyes closed, and Jefferson Hope moved no more.


	2. Don't We All Have Secrets?

"Go ahead without me; I'll meet you back at the flat. There are a few more things that I need to sort out with Lestrade." This wasn't strictly true; while he had already explained the magical sides to this case to the auror, he wanted to have a trot around on four legs again. Who knows, he might even introduce John to the pet cat he supposedly owned.

 

After a small pause, his medical instincts considering whether Sherlock was indeed fit to make his way home on his own, John nodded and strode off to hail a taxi.

 

Sherlock turned into a deserted alley, and sighed as he opened his eyes to a much lower view. The black tom cat stretched his spine in an elegant arch and flicked its ear. It had taken only a year and a half under the watchful eye of Professor McGonagall to become an animagus, making him the youngest person since The Marauders to learn the skill, and one of the fastest in at least 50 years. When he had first completed the transition from human to feline, it had been disorientating; now it was like slipping off a jacket. He had been thrilled to discover his second skin was a cat - the heightened senses, the extra agility and the smaller size was excellent for getting places otherwise inaccessible to him. Crime solving was a lot easier when you could sneak up on the culprit and catch them in the act. On the way back to Baker Street he was able to prevent two muggings and a robbery; a simple _Incarcerous_ and _Obliviate_ followed by a text to Lestrade and he was padding away with the closest thing to a smile that his feline features were capable of.

 

* * *

 

After the events of that evening, John had found himself once again immersed unbeknownst to anyone else in a world that he had long ago given up on. He got up and moved to his room, pulling a small box out from under his bed. There lay letters from his sister written on thick parchment, a small leather pouch of coins and several newspaper clippings. What was odd about the latter was that the pictures were moving.

 

It had broken John's heart when his Hogwarts letter never came. His sister Harry had gotten hers a few years before he turned 11, and he couldn't wait until he could learn how to turn teacups into animals and make objects fly. His parents, a witch and wizard, had always hoped that he was just a late bloomer; but he never showed any signs of magical ability. Finally admitting that their son was a Squib had driven his mum to drink, and his dad walked out on them soon after. Harry sent him letters, of course, thrilled to be in the same house as the famous Harry Potter, who arrived in her second year. John had followed the events after Voldemort had returned closely, terrified that his status as a Squib would mark him for execution.

 

When he was 15, his sister had suddenly Apparated into his bedroom, shaking like a leaf. Once she had calmed down enough to speak, thanks to a blanket and a large mug of tea spiked with a dash of Firewiskey, she told him what had happened. Voldemort had come to the school. She had been a member of some underground resistance group called The Order of the Phoenix, and she had gone to help fight him. Clara had gone with her and been badly injured by a werewolf, and the Healers at St Mungos were unsure if she was going to survive. Voldemort had been killed, but so had so many people she knew, from both school and the Order. After everything she had been through, everything she had seen, it hadn't been long before she was drowning out the screams in her head with a bottle of whiskey, even after the drink had killed their mother. Seeing what the magical world had done to his sister, John severed any ties he had with it, the only reminders hidden in this small wooden box. From under the newspaper clippings, he pulled out his mother's wand. He couldn't use it of course, but it was nice to have something solid to remember her as she had been before the drink by. Wrapping the wand back up in a handkerchief with the Ravenclaw eagle stitched in brilliant bronze thread, he returned it to the box and focused on what he had come up for.

 

He ruffled through the clippings until he found what he had been looking for. While old and slightly faded, the picture under the headline 'Ministry seeks educational reform' was the woman whose body had until recently been lying on the floor at Lauriston Gardens. Dolores Jane Umbridge. After seeing what role she had played in Voldemort's rise to power, he had little pity for her. That would explain the period of depression, sure signs of a stay at Azkaban before the dementors had been relieved of duty.

 

Placing the lid back on the box and returning it to under his bed, John padded downstairs for a mug of tea. Flicking on the tv, he settled down into his armchair, determined to not let the past evening faze him.

 

John looked up from his tea when he heard a soft bang from the door, just in time to see a black cat with slightly curly fur and bright green eyes stepping elegantly through the cat flap. The cat let out a deep meow, and trotted over and jumped up into Sherlock's chair; circling twice before curling up, still staring at John over his bushy tail. He shrugged, and pulled his laptop towards him, considering writing the events of the previous couple of hours up on his blog.

 

When John had finally started to type, the cat (he would have to ask Sherlock if it had a name) stretched, and jumped down to wind around John's ankles, a deep purr resonating from his chest. He shifted his computer to make room, and suddenly had a lap full of warm fur. His hand dropped down, and started to stroke the soft fur on the cat's head and behind the ears. The purring, if it was even possible, got even louder at the attention.

 

"I bet Sherlock doesn't give you nearly enough fuss. I'm amazed he even remembers to feed you; rushing around all the time, he barely even feeds himself." The cat let out another meow, butting his head up into John's palm.

 

After a few minutes, the cat's ears pricked up at something John couldn't hear. It sprang down from his lap and trotted over to the door to let himself out. Barely ten seconds passed before there was the unmistakable sound of the front door closing, followed by the pounding of feet on the seventeen steps leading up to their flat. The door opened to reveal Sherlock unwinding his dark blue scarf, his hair a little tousled from the wind outside.

 

"I assume you've hidden your gun? Don't pretend to look surprised, obviously it was you that shot the cabbie. And you better wash the powder burns off your fingers. I doubt you'd go to prison for it but best avoid the court case." John rolled his eyes.

 

"Of course I've hidden it, and I already cleaned my hands; I'm not stupid. What was it that gave me away?" Sherlock smiled, pleased at being given another chance to show off.

 

"The bullet that they dug out of the wall was from a hand gun. Kill shot over that distance from that kind of weapon - that's a crack shot, but not just a marksman; a fighter. His hands couldn't have shaken at all, so clearly acclimatised to violence. He didn't fire until I was in immediate danger, though, so strong moral principle. All this points to a man with a history of military service and nerves of steel, but also only resorts to acts of violence under extreme circumstances. Sound familiar?" John laughed, he couldn't help himself.

 

"I have to say, I never expected that this was how the day was going to go when I woke up this morning. Is it always like this?"

 

"More or less. Dinner?"

 

"Starving."


	3. Out of the Bag

Almost two months had passed since the affair with Jefferson Hope when John and Sherlock stumbled back into the flat after their latest case involving a Chinese smuggling ring that had almost gotten John and his date killed in a case of mistaken identity. Sherlock had turned up at the very last moment of course, having Apparated in his haste to rush to his friend's aide. Two months of living together without any slips that could give either of them away to the other.

They both collapsed into their respective armchairs, John threatening to pass out after the adrenaline from all of the excitement had worn off. In fact, he would have appeared unconscious to any observer, yet he could still see through his eyelashes. Sherlock, despite priding himself on noticing what others could not, could be spectacularly unobservant when his brain was otherwise preoccupied; such as now as he rode the high of another case solved and wondering where Shan would disappear off to. Believing John to be out, he produced his wand and told the tea to make itself as he usually did if John wasn't around.  He also dug out his small supply of pre-made potions and added a few drops of Mrs Hudson's signature calming draught into each mug. So caught up was he in his own thoughts that Sherlock hadn't noticed the scrape of John's chair as he suddenly stood up.

"I should have known that you of all people would be a bloody wizard. And you can't even be bothered to make a cup of tea without magic!" That got Sherlock's attention all right; causing him to jump so violently that the vial flew out of his hand and smashed on the tiles below.  This wasn't possible, John was a muggle, he was sure of it. So how on earth could he be talking about wizards and magic so calmly? He should be freaking out, or at the very least asking about a million questions all at once.

"How on earth...?"

"Do I know about magic?" John finished. "You mean you can't deduce it?"

"That's the thing. From the moment we met I thought you were a muggle. There are no blisters on your fingers that suggest the use of a wand, there are about a hundred spells and potions that would have healed your bullet wound, and still another several dozen spells that would have prevented the injury in the first place, that and a dozen more immediately obvious clues all point towards you being a muggle. "

John was tempted to let Sherlock stew for a bit longer, revelling in the rare feeling of knowing something that his flatmate didn't as he saw the wheels spinning ever faster in that brilliant brain to try and figure out something so unlikely that he would never have deduced it. After about another 30 seconds he took pity on the man and tapped his shoulder to get his attention.

"I'm a squib, Sherlock. We're rare enough so don't beat yourself up about not figuring that out." He gestured to the spilt potion. "Clean that up and then we can talk about this." Sherlock obliged, flourishing his wand and John watched as the shards of glass pulled themselves back together. The potion was a lost cause, so had to be Vanished. John sat a still shell-shocked detective down and handed him the tea, thankful for the potion that had been added.

"So, what do you want to know?" John braced himself for the onslaught of questions, and sure enough, Sherlock delivered.

" What houses were the rest of your family in?" It was an odd question to start with, John supposed. Then again, the Hogwarts' house that you were placed in could often tell a lot about you; possibly second only to the characteristics of a person's wand.

 "My mum was in Ravenclaw, and my dad was a Slytherin. He was always ambitious but his marks were terrible so he got her to tutor him. Harry was a Hufflepuff. How about you?" After what John knew about his flatmate after only a couple of months, he had his suspicions.

"I was a Slytherin, like your father. Before you say anything I just want to clarify that I never wanted anything to do with Voldemort. But surely there were other areas that you could still study; potions or herbology. You are a doctor after all." Of course he was a Slytherin; a Ravenclaw would definitely not delete information just because it wasn't 'useful', and he was much too lax about breaking rules. It would have been a close one, Harry had called them 'hat-stalls', and John smiled at the image of Sherlock locked in a fierce debate over which house he should be put into.

"I tried, but mum was never sober enough and Harry was only free during the school holidays. There were a few potion books lying around that I used to read but we never had the ingredients. And after what the war did to my sister I just gave up on magic; it's not like your lot ever cared much about what happened to me." That last sentence still stung a bit after all these years. It was well-known that the Ministry of Magic didn't even bother to keep a record of their birth, and John believed that it was this that had kept him under Voldemort's radar all those years.

Even with the many extraordinary things that he had seen since meeting Sherlock Holmes, it still amazed John how easily his old life that had never quite existed in the first place had caught up with him. 

"So now that you aren't hiding anymore, is there anything else I need to know?" This prompted a slightly sheepish look from Sherlock, making John roll his eyes. "What is it?"

"I'm an animagus." This of course meant nothing to John; neither of his parents had been one, and he and Harry had spoken very little of the wizarding world after Voldemort's return in her 6th year. His clearly puzzled expression was enough to prompt Sherlock.

"An animagus is a witch or wizard who, through often years of intensive study, gains the ability to transform into an animal at will. It's different to a simple transfiguration spell, such as you would have no doubt seen at home; as the person in question maintains full awareness of who they are and of their own magical abilities, allowing them to change back without external help or the use of a wand."

He then stood up and before John's astonished gaze, shrank down until in his place stood the small black tom-cat that would occasionally potter about the flat or curl up on John's lap when Sherlock was apparently out doing more research at the lab in St. Bart's. That the great Sherlock Holmes would even deign to show affection even as a different species was strangely amusing to John, that is after the initial surprise at this latest insight into just how much magic could accomplish wore off enough for other thoughts to form. John just brushed the thought aside though, as from experience he had noticed that the cool, calculating sociopath that he claimed to be was an act put on for the police; anyone who had seen how affectionate he could be towards Mrs Hudson would see that.  John had leant a while back not to be too surprised by anything that Sherlock did so as not to inflate his already impressive ego, even if he was in the habit of occasionally strolling around London disguised as a cat. He simply shrugged it off and reached for his tea as Sherlock summoned a packed of Hobnobs from the kitchen cupboard.


End file.
